Seeker, My comment about the wheels is specifically related to the rear hub. OPs son is likely not that big given the size of bike, so rim strength and spoke count shouldn’t be an issue. The issue will be the fact that this bike is likely running a freewheel and old style hub rather than a modern freehub style hub. The older style has a much longer axle reach between bearings and frame dropout. This ends up being a major weak point in the wheel. Most often, you bend an axle. Sometimes you end up with a cracked hub shell where the bearing cup is. Then you’re Really screwed.

The chain stays look plenty long enough. Toe overlap isn’t a big deal as long as you don’t regularly try to pedal through semi-sharp low speed turns.